Method of making corrugated sponge rubber



Jan. 31, 1939. R MINOR 2,145,731

METHOD OF MAKING CORRUGATED SPONGE RUBBER Filed May 7, 1957 if I AINVENTOR. /a HENRY R. N/NoR ATTORNEYS Patented Jan. 31,1939

UNITED STATES PATENT OFFICE METHOD OF MAKING CORRUGATED SPONGE RUBBERApplication May 7, 1937, Serial No. 141,316

7 Claims.

My invention relates to a method of manufacturing sponge rubber and inparticular the manufacture of sponge rubberin a variety of forms such ascorrugations.

It is the object of my invention to provide a method by which rubberstock of the minimum thickness in which it can be suitably and readilyhandled can be converted into rubber sponge from stock which stretchesto a thickness prior to 3 being sponged that could not'b'e handled.

It is my object to provide a method by which thin rubber stock of theminimum thickness enabling it to be handled can be laid upon the formwhich it is to assume as sponge; which thereafter upon being heated willconform and stretch over the form of the mold; andv by a continuation ofthe method, will assume a relatively thick sponge character in the shapeof the mold.

It is a further object to provide a method in which the configurationcan be imparted to the sponge both on the top and bottom thereof by onlyhaving a bottom supporting mold.

It is a further object to provide a method in which these bottom moldscan be nested one over the other in the heater and the sponge producedin large quantities with this simple 'apparatus in a common heater.

Referring to the drawing:

Figure 1 illustrates diagrammatically the side of a mold for makingcorrugated sponge rubber with a layer of 50-gauge rubber stock on top ofthe mold as it is laid'in position prior to practicing the process.

Figure 2 is a similar view showing the rubber stock heated sufllcientlyto sink within the curvature of the mold and to stretch for that purposeto a thickness that is uniform over the mold but which, if the rubberstock was handled, would prove insufllciently strong to permitsatisfactory 350 the line 55 of Figure 4.

Referring to the drawing, I designates a corrugated metal mold. One ofthe advantages of my invention is that the mold may be made of avariety-oi materials and need not be a structure 55 of great strength.,It can be made of thinsheet.

metal, a die casting or casting of any type, and I have successfullyused a mold of rubber or combined rubber and fabric. This configuratedmember I is placed within a'container 2 which is provided with apertures3 of any desired number or location, depending upon the character of thesponge that is to be produced, as more fully set forth, explained andclaimed in my co-pending application Ser. No.- 137,130, filed April 15,1937.

The rubber is preferably supplied in a -gauge stock sheet 4. This sheetis approximately the lightest that can be handled with facility. It islaid across the surface of the configurations 5 of the configuratedmember I. In practice I place a number of these molds and the containers2 on shelves 6 of a truck I or upon shelves 8 on the side walls of anautoclave 9. The truck has wheels in travelling on the tracks II in thebottom of the autoclave. The door 121s then closed. The autoclave isthen provided with a steam 2O jacket 13 to which steam is admittedthrough the pipe l4. 15 indicates a condensation trap in the exit line16. i1 is a thermometer, IS a steam gauge and I! an autoclave pressuregauge. Carbon dioxide is supplied to the chamber by the pipe 20controlled by the valve 21. It is released from the chamber through thedischarge line 22 controlled by the valve 23 and through the nozzle 24.

The preferred process is that outlined in my 30 co-pending applicationSer. No. 137,129, filed April 15, 1937. The article produced by thispresent method is shown in my application Ser. No. 137,322, filed April16, 1937.

When the rubber stock is placed within the autoclave, the stock ispreliminarily impregnated and heated at a temperature below 140 degreesFahrenheit and with a gas pressure from 100 to' 1'70 pounds. Due to thethinness of the stock, it is possible to reduce this impregnation periodto 40 only 10 to 15 minutes and during that period, the stock 4 sinksdown and follows the configurations 5 as at to in Figure 2. In doing soit stretches and becomes thinner. The stock is so thin that it could notbe handled in such thinness in sheet form. However, it is thick enoughto produce the sponge product desired and one of -the advantages of myprocess, aswell as one of its features, is to be able to utilize a sheetof rubber stock that is so thin it cannot be manually handled, and to dothis by placing over the configurations a sheet that can be handled andthen permitting that sheet during its initial stage of treatment tofollow the configurations of the moldand in doing so to automaticallystretch the cheapest type of configurated molds and to" have a largenumber of them for simultaneous treatment and sponging in a commonautoclave, I

all without a prohibitive inventory in molds.

Heretofore the use of molds, particularly with the higher pressuregases, has necessitated a very expensive investment in high pressureequipment and in the very rigid heavy molds necessary with suchequipment. While my process and method are adaptable to such equipment,nevertheless it is not necessary.

After this preliminary heating and impregnation period of 10 to 15minutes, I then turn on the steam to raise the, heat of the rubberwithout causing an expansion other than'the expansion of the gas cellsin the rubber and continue heating until the rubber is thoroughlysoftened.

I also increase the gas pressure to a maximum of approximately 180pounds and then release the gas while continuing the in'crease oftemperature to approximately 260 degrees Fahrenheit, but so adjustingthe release of the gas-that it is substantially completed" before orshortly after the rubber takes its final set of vulcanizae tion, therebyusing the expansion of the gas to secure the maximum of sponging of therubber with the minimum of rubberstock and the mini-' mum of gas.

Other gases may be employed other than carbon dioxide, but I prefer itfor the purposes of this invention.

I therefore provide a process and a method of sponging rubber in which(a) I lay the thinnest sheet of stock that can be handled over the formto which the sponge is to be molded; (b) I simul taneously heat andpreferably also impregnate with gas such sheet so that it issufficiently plastic to follow the configurations of themold and touniformly thin itself for that purpose to a thickness which would makeit impossible of manual handling. I then increase the temperature andthe pressure to bring about suitable sponging of the rubber in theconfiguration desired and I have found that only the bottom mold isrequired due to the fact that the upper surface will evenly follow theconfigurations of the bottom mold without the necessity of a top mold,thereby further economizing on mold equipment.

The sharp drop-off in maximum pressure and 'the'continued heating mustbe so adjusted by the userof this method so that the heat applied is notso great as to cause the rubber to set prior to the completion of therelease of the gas, and the heat supplied must be sufiicient to preventthe gas .I claim as new and desire to secure by Letters Patent, is: a

1.-In a method of making a conflgurated sponge rubber product, the stepsof providing a closed chamber having a mold part therein provided withconfigurations of such depths and widths that a sheet of rubber may sagdown into the depression thereof and conform thereto when laid thereonand treated as hereinafter described; laying a sheet of rubber on saidmold part, heating and introducing gas under. pressure into said chamberto cause the" rubber sheet to absorb gas and conform to theconfiguration of the mold part, regulating the heat and pressure withinsaid chamber tocause the rubber to sponge and to completely fill thedepressions, and to cause the upper surface of the rubber to have apuffed irregular formation of the general configuration of the moldpart.

2. In a method of making a configurated sponge rubber product, the stepsof providing a closed chamber having a mold part therein provided with aplurality of corrugations of such depths and widths that a sheet ofrubber may sag down into the depressions thereof and conform theretowhen laid thereon and treated as hereinafter described, laying a sheetof rubber on said corrugated mold part, heating and introducing gasunder-pressure into said chamber to cause the rubber sheet to absorb gasand conform to the corrugations of the mold part, regulating the heatand pressure within said chamber to cause the rubber to sponge and tocompletely fill the depressions, and to cause the upper surface of therubberto have a puffed irregular formation of the general configurationof the mold part.

3. In a'method of making a configurated sponge rubber product, the stepsof providing a closed chamber having a mold part therein provided with aplurality of corrugations of such depthsand widths that a sheet ofrubber may sag down into the depressions thereof and conform theretowhen laid thereon and treated as hereinafter described, laying a sheetof rubber on said corrugated mold part, heating and introducing gasunder pressure into said chamber to cause the rubber sheet to absorb gasand conform to the corrugations of the mold part, regulating the heatand pressure within said chamber to' cause the rubber to sponge and tocompletely fill the depressions, and to cause the upper surface of therubber to havea puffed irregular formation of the general configurationof the mold part, but to an insufficient extent to cause the rubber toexpand to a point where the rubber engages the top of the chamber.

In a method of making a configurated sponge rubber product, the steps ofproviding a closed chamber having a mold part. therein. provided withconfigurations of such depths and widths that a sheet of rubber may sagdown into the desponge rubber product, the steps of providing a closedchamber having a' mold part therein ,provided with corrugations of suchdepths andwidths that a sheet of rubber may sag down into the 5. 'In amethod of making a configurated depressions thereof and conform theretowhen laid thereon and treated as hereinafter described; laying the sheetof rubber of said mold part, heating and introducing gas under thepressure into said chamber to cause the rubber sheet to absorb gas andsimultaneously regulating the heat and pressure within said chamber tocause the rubber to sponge and to completely fill the depressions, andto cause the upper surface of the rubber to have a pufled corrugatedformation of the general configuration of the mold part.

6. In a method of making aconflgurated sponge rubber product, the stepsof providing a closed chamber having a mold part therein provided withcorrugations of such depths and widths that a sheet of rubber may sagdown into the depressions thereof and conform thereto when laid thereonand treated as hereinafter described; laying the sheet of rubber on saidmold part, heating and introducing gas under the pressure into, saidchamber to cause the rubber sheet to absorb gas and simultaneouslyregulating the heat and pressure within said chamber to cause the rubberto sponge and to completely. flll the depressions. and to cause theupper surface of therubbertohaveoorrulatodformationofthe generalconfiguration of the mold part, but without expanding the sponged rubberto a point where the sponging rubber engages the top of the chamber.

7. In a method of making a conflgurated sponge rubbervproduct, the stepsof providing a closed chamber having a mold part therein provided withcorrugations of such depths and widths that a sheet of rubber may'sagdown into the depressions thereof and conform thereto when laid thereonwhen treated as hereinafter described; laying a sheet of rubber freefrom sponge ingredients on said mold part, heating and introducing gasunder pressure into said chamber to cause the rubber sheet to absorb gasand to conform to the corrugations of the mold part, simultaneouslyregulating the heat within said chamber to cause the rubber to spongeand completely fill the corrugations and to cause the upper surface ofthe rubber to have a puffed formation of the general configuration ofthe mold part, but

without expanding the sponged rubber to a point where the sponged rubberengages the top of the chamber.

HENRY R. MINOR.

